1. Field of the Invention
The present invention relates to an agricultural electric vehicle and, more particularly, to a load-sensitive automatic transmission system for an agricultural electric vehicle, which can automatically perform the speed change by detecting a motor load of an electric vehicle powered by a motor.
2. Discussion of Related Art
Generally, an electric vehicle is powered by electricity, which produces no emissions, compared to conventional vehicles using gasoline or natural gas, and has a structure shown in FIG. 7.
FIG. 7 is a schematic diagram illustrating the structure of a conventional electric vehicle, which generally comprises a battery 10, a motor 20 for generating a driving force using the electric power of the battery 10, a differential gear 50 for transmitting the driving force of the motor 20 to wheels 51, and a control unit 60 including a power control unit (PCU) and a power relay assembly (PRA) for controlling the current supplied to the motor 20.
Since the rotational direction (forward or reverse rotation) and rotational speed of the motor 20 in the above-described motor-driven vehicle are controlled by a current signal, the motor 20 has advantages that the forward/reverse movement and the speed control are convenient.
Especially, in the motor-driven vehicle, the use of a forward/reverse gear employed in an engine-driven vehicle, a clutch mechanism for cutting off the power in an idle state, etc., is not required, and thus it is possible to reduce the weight of the vehicle and the manufacturing cost.
However, the above-described electric vehicle is difficult to achieve a high torque due to the nature of the motor, and thus cannot be used as a working vehicle for agriculture or construction.
Due to these features, the use of the electric vehicle has been limited to driving on city streets.